Scattered toner shield device in electrophotographic copying machine

ABSTRACT

A scattered toner shield device in an electrophotographic copying machine which includes a photosensitive medium having a dielectric surface layer and a photoconductive layer, primary charger means, contemporaneous exposure and discharge means, a developing station comprising overall exposure means and developing means, and if required, a transfer station. The shield device comprises an insulative shield member disposed between the contemporaneous exposure and discharge means and the developing station and in contact with the photosensitive medium. The shield device may further comprise a second insulative shield member disposed between the developing station and the transfer station.

United States Patent 1191 Takahashi et al. June 4, 1974 SCATTERED TONER SHIELD DEVICE 1N 1635.196 1/1972 Tsilihcs 118/637 3.685.486 8/1973 ll8/637 gkfgg COPYIN('- 3.695.224 10/197: Royka 118/637 Inventors? Takflhashii jiro Primary E.\'amir1erSamuel S. Matthews Kadowak" h of Tlkyoi Tsukasa Assistant Eraminer-Kenncth C. Hutchison Kuge, Kawasak'r of Japan Attorney, Agent, or Firm-Fitzpatrick, Celia. Harper [73] Assignee: Canon Kabushiki Kaisha, Tokyo, & Scmto Japan 221 Filed: Aug. 17,1972 S d Z Z scattere toner 5 ie evice in an electrophoto- [zl Appl' 28]4l4 graphic copying machine which includes a photosensitive medium having a dielectric surface layer and a [30] Foreign Application Priority Data photoconductive layer, primary charger means, con- Aug 27 Japan 46 65677 temporaneous exposure and discharge means, a developing station comprising overall exposure means and [52] Cl I I I v 355/3 DD 118/637 developing means, and if required, a transfer station. [51] Int. Cl. I h 63 5 The shield device comprises an insulative shield mem- [58] Field 118/637 ber disposed between the contemporaneous exposure I and discharge means and the developing station and in [56] References Cited contact with the photosensitive medium. The shield device may further comprise a second insulative shield UNITED STATES PATENTS member disposed between the developing station and 2.998.802 9/1961 Harris et :11. 118/637 the t f Station 3,424.l3l l/l969 Ascr et al. 3,620,191 11/1971 Lyles 118/637 2 Claims. 4 Drawing Figures v l SCATTERED TONER SHIELD DEVICE IN ELECTROPHOTOGRAPHIC COPYING MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a shield device for preventing scattering of developer in electrophotographic copying machines. I

2. Description of the Prior Art In electrophotographic copying machines, especially of the dry development type, developer or toner may be scattered beyond the developing station and may stick to the discharge electrode in the discharger means and cause an irregular charging or discharging effect and/or stain the'other parts of the machine. Such toner may sometimes fly out to the exterior of the machine to pollute the atmosphere and thusharm the operator's health. Such scattering of toner forms a serial disadvantage of the dry type electrophotographic copying machines. i

' SUMMARY OF THE INVENTION The presentinvention aims at the solution of the above-noted problem. More specifically an object of, the present invention is to prevent toner or developer from scattering beyond the developing station during development in an electrophotographic copying machine: wherein an electrostatic latentimage is formed on a photosensitive medium comprisinga photoconductive substrate, a photoconductive layer and a dielectric layer or, on a photosensitive medium basically comprising a photoconductive layer sandwiched between dielectric layers; wherein'theimage is formed by charging such photosensitive medium. and by contemporaneously applying original image light and discharge to such medium and then subjecting such medium to overall exposure; and, whereafter the latent image is dry-developed as by a method using a cascade. magnet brush or'fur brush, and if required, the developed image may be transferred and fixed.

According to the present invention, an insulating member maybe disposed between the developing station and the electrostatic latentimage forming station andbrought into contact with the photosensitive medium so as not to disturb the electrostatic latent'image formed thereon, .and such insulating blocks any toner which tends to scatter from the developing station to the electrostatic latent image forming station.

A further shield member for preventing scattering of toner may be provided between the developing station and the subsequent transfer or fixing station. These shield members can prevent any toner from scattering from the developing station to the other parts or the exlayer surface of the photosensitive medium. scattering BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will be described in detail hereunder with reference to the accompanying drawings, in which:

FIG. I is a schematic view of a xerographic drum type electrophotographic copying machine to which the present invention is applied and showing the arrangement of various process stations;

FIG. 2 is a similar view of the copying machine which uses a three-layer photosensitive drum;

FIG. 3 illustrates an application of the present invention to a drum type electrophotographic copying machinewhich uses a transfer roll; and

FIG. 4 illustrates a further application of the present invention to a copying machine which utilizes-a corona transfer process. 7

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is schematically showna xerographic drum type electrophotographic copying machine which includes a photosensitive drum I having a photosensitive surface surrounded by various process stations such as charging station 2, exposure station 3, developing station 4, transfer station 5 and cleaning station6. Through these successive processes. a toner image is transferred to atransfer medium'7.

In the developing station, the toner in the developer container may be stirred and scattered by any of various methods using a magnet brush, fur brush or the like so as to cause the toner to be deposited'on the electrostatic latent image on the photosensitive medium and thereby visualize such latent image. The developer container is hermetically sealed as far as possible, but in view of the fact that the fore and rear portions thereof as viewed in the direction of rotation of the photosensitive drum 1 should not be in sliding contact with the surface of the drum, there are provided slight clearances at such portions between the developer container cause this would disturb the electrostatic latent image and the photosensitive drum, through which clearances some of the toner in the container may unavoidably scatter beyond the developing station.

The present invention, therefore, intends to block the toner so scattered from the developing container and keep such scatteredtoner within the developing station, thus shielding other parts of the machine from suchscattered toner. To that end, the present invention provides an insulating member 8'disposed between the developing station 4 and the exposure station (or latent image forming station) 3 and in contact with the surface of the photosensitive medium was not to disturb an electrostatic latent image formed on the photosensitive medium.

The insulating member 8 may be formed of Maylar I (tradename), for example, and may have a thickness of the order of 0.02 mm, a length slightly greater than the axial length of the photosensitive drum 1, and a width of the order 'of 20 mm. The insulating member 8 may be supported by a support member 9 at a point spaced apart about mm from the photosensitive drum, and has a portion extending from the support member 9 into contact with the photosensitive drum 1. Between the support member 9 and the developer container, there may be mounted a shield plate 10 so as to define an interior space 11. I

With such an arrangement. any toner which tends to clearances scatter from the developing station 4 toward the exposure station 3 may be blocked by the insulating member 8 and accumulated in thespace 11, so that the other parts of the machine may be shielded from the scattered toner. The use of Mayar film for the insulating member 8 is effective in that no disturbance is imparted to the electrostatic latent image formed on the photosensitive drum. The clearance provided be-- tween the photosensitive drum 1 and the developer container at the fore and rear portions thereof as viewed in the direction of rotation of the drum may be filled with suitable packing.

In a system basically using a three-layer photosensi tive medium comprising a conductive layer, a photoconductive layer and a transparent dielectric layer, or a system employing, in addition thereto, such processes as primary charging 2, contemporaneous exposure and AC or DC discharge 12, and overall exposure 13, as

shown in FIG. 2, a complete electrostatic latent image.

may be formed by overall exposure with both the light and dark areas of the exposed image being substantially at zero potential after discharge and before overall exposure.

In this case, therefore, the aforesaid insulating member 8 may effectively be provided between the contemporaneous exposure and discharge station 12 and the overall exposure station 13 in order that the electrostatic latent image may not be disturbed. In this regard, the potential on the surface of thephotosensitive me dium after discharge need not be exactly zero, but a potential in the vicinity of zero which would not disturb the latent image may also be available to carry out the present invention.

In the system as shown in H6. 2, the contemporaneous exposure and discharge station 12 is located near the developing station 4, and this has often permitted toner to enter the station 12 through an opening thereof which is on the opposite side to a lighttransmitting glass 14, thus staining a discharge electrode 15 disposed within the station 12.

In any of the systems as shown in FIGS. 1 and 2, use is often made of a transfer process utilizing a transfer roll 6 as shown in FIG. 3. In such cases, the aforesaid Mylar film 8 or a slightly thicker resilient sheet 17 may be disposed in contact with the transfer roll 16 at the side thereof which is adjacent to the developing station 4, and a transfer medium 7 may be passed under the resilient sheet and guided by the transfer roll 16, whereby any toner which tends to scatter from the developer container toward the transfer station may be blocked.

A greater effectiveness will be provided if the insulating member 8 and the sheet 17 are connected together by a shield plate 18 so as to physically isolate the developing station 4 in the machine body. Numeral l9 designated a transfer roll cleaner.

Where the image transfer is carried out by the use of a corona charger 21 as shown in FIG. 4, a similar resilient sheet 17 may be disposed in contact with a guide roll 20 with a transfer medium intervening therebetween, thereby preventing the scattering of the toner as well as achieving the guidance of the transfer medium.

As has been described above, the present invention provides a scattered toner shield member before and behind the developing station, to thereby achieve excellent effects in preventing the reduced performance such as irregular charging effects resulting from a stained charger in the machine and also preventing the pollution of the atmosphere around the machine.

The overall exposure means disposed in the developing station may be stained more or less, but this will form no problem in practice because use is made of a light source having an illumination as high as about 10 to times the intensity of light required for exposure.

We claim:

1. An electrophotographic copying machine comprising a photosensitive medium having an insulating surface layer and a photoconductive layer, charger means for uniformly charging said photosensitive medium, means for applying an original light image and a discharge contemporaneously, a developing station comprising blanket exposure means and developing means, and a shield device comprising a scattered toner shield member of insulative material disposed in contact with said photosensitive medium between said means for applying an original light image and discharge and said developing station.

2. An electrophotographic copying machine including a photosensitive medium having an insulating surface layer and a photoconductive layer, charger means peripherally opposed to said photosensitive medium for applying a charge thereto, means for applying an original light image and a discharge contemporaneously, a developing station comprising blanket exposure means and dry type developing means, and a transfer station including means for transferring a developed image to a transfer medium, and a shield device comprising a first scattered developer shield member of insulative material disposed in contact with said photosensitive medium between said means for applying an original light image and discharge and said developing station, and a second scattered developer shield member disposed between said developing station and said transfer station to block any scattered toner and to guide a said transfer medium to said transfer station.

I UNITED STATES PATElIT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,8l4,5l 5 Dated June 4, 1974 Inventor(s) TORU TAKAHASHI," ET AL.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 18, "serial" should read serious-;

Column 1, line 46 after "insulating" insert member; Column 2 line 63, "Maylar" should read -Mylar-; v

Column 3, line 8, "clearances" should be deleted;

Column 3, line 12, "Mayar" should read -Mylar--;

Column 3, line 15, "clearance" should read -clearances;

Column 4, line 5, "designated" should read -designates.

Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMWDC combing us. sovsnuuzu-r PRINTING omcz: I969 o-ssg-su.

Dnted June 1, 1974 Patent No g iilfl Inventor(s) TORU TAKAHASHI ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 18, "serial" should read -serious;

Column 1, line 46, after "insulating" insert -member-;

Column 2 line 63, "Maylar" should read Mylar;

Column 3, line 8, "clearances" should be deleted;

Column 3, line 12, "Mayar" should read Mylar;

Column 3, line 15, "clearance" should read --clearances--;

Column 4, line 5, "designated" should read designates-.

Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON C. MARSHALL DANN Arresting Officer Commissioner of Patents FORM po'wso T USCOMM-DC 6O376-P6D U.S. GOVERNMENT PRINTING OFFICE I 969 0366'33, 

1. An electrophotographic copyinG machine comprising a photosensitive medium having an insulating surface layer and a photoconductive layer, charger means for uniformly charging said photosensitive medium, means for applying an original light image and a discharge contemporaneously, a developing station comprising blanket exposure means and developing means, and a shield device comprising a scattered toner shield member of insulative material disposed in contact with said photosensitive medium between said means for applying an original light image and discharge and said developing station.
 2. An electrophotographic copying machine including a photosensitive medium having an insulating surface layer and a photoconductive layer, charger means peripherally opposed to said photosensitive medium for applying a charge thereto, means for applying an original light image and a discharge contemporaneously, a developing station comprising blanket exposure means and dry type developing means, and a transfer station including means for transferring a developed image to a transfer medium, and a shield device comprising a first scattered developer shield member of insulative material disposed in contact with said photosensitive medium between said means for applying an original light image and discharge and said developing station, and a second scattered developer shield member disposed between said developing station and said transfer station to block any scattered toner and to guide a said transfer medium to said transfer station. 